The present invention relates to an adjustable wrench. The adjustable wrench can continuously rotate a nut without repeatedly drawing up the wrench and fitting the wrench onto the nut. In addition, a switch button can be switched to change the rotational direction without reversing the adjustable wrench.
FIG. 8 shows a conventional adjustable wrench having a fixed jaw 8 and a movable jaw 81. The fixed jaw 8 is equipped with a thread rod 82. A grip 83 is connected with lower side of the fixed jaw 8. A lower side of the movable jaw 81 is equipped with a rack 84 meshing with the thread rod 82 for adjusting the gap between the fixed jaw 8 and the movable jaw 81 in accordance with the sizes of different nuts to be tightened or untightened. There is an inconvenience existing in use of such adjustable wrench as follows: in the case that the adjustable wrench or the nut is limited in position, for example, the nut is positioned in a dent, the adjustable wrench will be unable to totally untighten or tighten the nut at one time. Under such circumstance, each time after the wrench is fitted onto two opposite sides of the nut and rotate the same by a certain angle, the wrench must be drawn up and then fitted onto two other opposite sides of the nut to further rotate the same by a certain angle. Such procedure must be repeatedly performed. Therefore, with respect to a general nut with a locking depth at least three times the pitch, it is necessary to rotate the nut through over 1080 degrees (rotating three circles=360 degrees.times.3) for tightening or untightening the nut. In case each time the nut can be rotated through 60 degrees, it will take 18 times repeatedly fitting actions. Such operation is quite inconvenient and will lead to a low working efficiency.
FIGS. 9 to 11 show another type of adjustable wrench having a fixed jaw 9 and a movable jaw 91. The fixed jaw 9 is equipped with a thread rod 92. A grip 93 is connected with lower side of the fixed jaw 9. A lower side of the movable jaw 91 is equipped with a rack 94. The movable jaw 91 is formed with a slide channel 95 in which a slide block 96 is disposed. The slide block 96 is disposed with a spring 97 positioned between the movable jaw 91 and the slide block 96. After the slide block 96 is moved within the slide channel 95, the spring 97 serves to restore the slide block 96 to its home position. In addition, the rack 94 meshes with the thread rod 92 for adjusting the gap between the fixed jaw 9 and the movable jaw 91 in accordance with the size of the nut. After the nut is rotated through a certain angle, the adjustable wrench is turned back, whereby the slide block 96 is pushed by the nut by reason that the distance between opposite angles is larger than the distance between opposite sides. Therefore, the slide block 96 slides outward until the slide block 96 and the fixed jaw 9 pass over the opposite angle. At this time, the spring 97 restores the slide block 96 to its home position and the wrench can be again forced to rotate the nut.
In use of such adjustable wrench, the repeated fitting actions are omitted. However, in the case that the tightening operation is converted into the untightening-operation, the wrench must be reversed. It is inconvenient to perform such action, especially when the nut is positioned in a dent and can be hardly fitted with the wrench. Moreover, in a unified operation, in order to control and unify the pre-load of the nut and bolt, the nut is often first tightened and then loosened by, for example, one third circle. Under such circumstance, immediately after the nut is tightened, the wrench must be reversed and then again fitted with the nut to untighten the same. Such procedure is quite troublesome and will lead to low working efficiency.